15 research outputs found
Constraint-based Run-time State Migration for Live Modeling
Live modeling enables modelers to incrementally update models as they are running and get immediate feedback about the impact of their changes. Changes introduced in a model may trigger inconsistencies between the model and its run-time state (e.g., deleting the current state in a statemachine); effectively requiring to migrate the run-time state to comply with the updated model. In this paper, we introduce an approach that enables to automatically migrate such runtime state based on declarative constraints defined by the language designer. We illustrate the approach using Nextep, a meta-modeling language for defining invariants and migration constraints on run-time state models. When a model changes, Nextep employs model finding techniques, backed by a solver, to automatically infer a new run-time model that satisfies the declared constraints. We apply Nextep to define migration strategies for two DSLs, and report on its expressiveness and performance
Non-Monochromatic and Conflict-Free Coloring on Tree Spaces and Planar Network Spaces
It is well known that any set of n intervals in admits a
non-monochromatic coloring with two colors and a conflict-free coloring with
three colors. We investigate generalizations of this result to colorings of
objects in more complex 1-dimensional spaces, namely so-called tree spaces and
planar network spaces
On computing tree and path decompositions with metric constraints on the bags
We here investigate on the complexity of computing the \emph{tree-length} and
the \emph{tree-breadth} of any graph , that are respectively the best
possible upper-bounds on the diameter and the radius of the bags in a tree
decomposition of . \emph{Path-length} and \emph{path-breadth} are similarly
defined and studied for path decompositions. So far, it was already known that
tree-length is NP-hard to compute. We here prove it is also the case for
tree-breadth, path-length and path-breadth. Furthermore, we provide a more
detailed analysis on the complexity of computing the tree-breadth. In
particular, we show that graphs with tree-breadth one are in some sense the
hardest instances for the problem of computing the tree-breadth. We give new
properties of graphs with tree-breadth one. Then we use these properties in
order to recognize in polynomial-time all graphs with tree-breadth one that are
planar or bipartite graphs. On the way, we relate tree-breadth with the notion
of \emph{-good} tree decompositions (for ), that have been introduced
in former work for routing. As a byproduct of the above relation, we prove that
deciding on the existence of a -good tree decomposition is NP-complete (even
if ). All this answers open questions from the literature.Comment: 50 pages, 39 figure